The subject can fly at a speed of 60 feet (or 40 feet if it wears medium or heavy armor, or if it carries a medium or heavy load). It can ascend at half speed and descend at double speed, and its maneuverability is good.

Using a fly spell requires only as much concentration as walking, so the subject can attack or cast spells normally. The subject of a fly spell can charge but not run, and it cannot carry aloft more weight than its maximum load, plus any armor it wears. The subject gains a bonus on Fly skill checks equal to 1/2 your caster level.

Should the spell duration expire while the subject is still aloft, the magic fails slowly. The subject floats downward 60 feet per round for 1d6 rounds. If it reaches the ground in that amount of time, it lands safely. If not, it falls the rest of the distance, taking 1d6 points of damage per 10 feet of fall. Since dispelling a spell effectively ends it, the subject also descends safely in this way if the fly spell is dispelled, but not if it is negated by an antimagic field.

When a character or creature is flying, and that creature decides to ascend at a 45 degree angle, the rules states that it moves at half speed? Do the rules for diagonal square counting still apply when moving up diagonally in this way?

No. Since the game is generally assumed to be played in two dimensions, even when representing three dimensional combat, the rules for ascending are handled by the speed reduction instead of asking players and GMs to ascertain the diagonal vertical movement.

Mythic Fly

The fly speed changes to 120 feet (or 80 feet if the target is wearing medium or heavy armor, or carrying a medium or heavy load) with perfect maneuverability. When the duration expires, the target is protected by feather fall for a number of rounds equal to your caster level.

Augmented (3rd): If you expend two uses of mythic power, the target adds your tier on Reflex saves and as a dodge bonus to AC. It gains these bonuses only while flying.

Note…

Paizo designer Sean K. Reynolds designed some completely unofficial variants of the fly spell on his personal website. Yes, these are COMPLETELY unofficial. Consult your GM to confirm if these might be allowed!

“Here are three variants of the fly spell from different schools. Each of them has a weakness, drawback, or some other element that makes them less effective or powerful than the transmutation form of the spell), but they’re still viable options for thematic spellcasters or specialist wizards who chose transmutation as a prohibited school.”

*We adapted the necromantic variant to be compatible with the Pathfinder rules.

This spell functions like fly, except that rather than being sustained by magic, you conjure a Small flying outsider that carries the target and follows his mental commands.

The outsider has hit dice (d8s) equal to half your caster level and 4 hit points per hit die. The outsider is a separate creatures for the purpose of all effects (such as targeted and area effects). It uses the target creature’s saving throw bonuses and has improved evasion. It is subject to all effects that target outsiders (such as magic circle spells, which prevent it from entering or carrying the target into that area). If the outsider is killed, the spell ends (carrying the target safely to the ground as explained in the fly spell).

When you use a summoning spell to summon an air, chaotic, earth, evil, fire, good, lawful, or water creature, it is a spell of that type. When you summon the creature, you decide if it is a celestial (angel, avoral, or guardinal), fiend (daemon, demon, or devil), or elemental (air or fire); this choice has no effect on the creature’s abilities (though if you have an ability that augments or extends spells you cast that summon certain creatures it has the normal effect).

This spell functions like fly, except that rather than being sustained by magic, the target grows a pair of wings made of shadow that allows him to fly.

The wings work best in shadowy illumination or darkness, where they allow the target to fly as described in the fly spell. In normal light the creature is reduced to half speed; in bright light (such as full sunlight or in the radius of a daylight spell) the creature cannot fly but still falls safely as if under the effects of a feather fall spell.

This spell functions like fly, except that rather than being sustained by magic, the target grows a pair of batlike or birdlike undead wings that allows them to fly.

The wings have hit dice (d12s) equal to half your caster level and 6 hit points per hit die. The wings are a separate creature for the purpose of all effects (such as targeted and area effects). They use the target’s saving throw bonuses, and the target’s defenses (such as protection from energy) apply to the wings. The wings are destroyed, the spell ends (carrying the target safely to the ground as explained in the fly spell).

The wings are vulnerable to turning or command undead attempts. If effected by the Turn Undead feat, the wings flee (bringing the target with them) on the target’s turn for the duration of the turning. If effected by the Command Undead feat or a spell like command undead, the wings cower and refuse to move the target from its present location (though this doesn’t prevent the target from using other methods to move or performing actions). If commanded, the commanding creature can direct where the target flies but does not otherwise control the target.